On a typical day, Chris Baker, a senior technician at Crutchfield, the electronics retailer, takes five calls from angry customers who say their televisions are not delivering the picture they paid for. In most cases, they are right.

Take the customer with a new $1,500 26-inch Aquos high-definition television who called the company's headquarters in Charlottesville, Va., last month. "He was disappointed with how most everything looked," Mr. Baker said.

It turns out the customer's set had been hooked up to a standard-definition cable box, and with a low-grade cable at that. Mr. Baker gave him instructions on how to tune in a high-definition broadcast over the air. When a PBS show about polar bears appeared on the screen, "he had one of those 'Oh my God!' moments," Mr. Baker said.

For consumers puzzled about the lackluster picture on their new TV's, the problem is rarely a defect in the set. Many high-definition TV owners don't know they need a special cable box or satellite receiver to view HD programs.

"I have friends who say, 'Look at my display. Doesn't it look great?' And I say, 'It would look better in high definition,' " said Kevin Zarow, vice president for marketing and product development at Marantz, a maker of home entertainment equipment.

It's not just new HD sets that can have less-than-optimal images. Owners of standard sets often fail to make the few simple adjustments that can make their TV pictures more true.

Virtually every TV comes from the factory with the color levels set incorrectly. Sometimes the necessary cables are not included in the packing box. And sometimes additional equipment may be required. Still, most improvements can be made easily, often at little or no cost.

A picture may be poor because the set is hooked to the wrong kind of cable input. Although some TV's can get a signal through any of seven types of cables, only three of them - component, DVI and HDMI cables - carry high-definition signals. A common mistake is using an S-video cable from a conventional TV on an HD set.

The quality of the cable also matters. New gear often comes with cheap ones that can make the picture fuzzy or snowy. Cables should be heavy enough to carry an unrestricted signal, shielded from interference, and have sturdy plugs.

Adjusting the color is crucial because manufacturers usually set the colors to high brightness to grab attention in the store.

They adjust the set "so it will scream at you when you come in the door," said Joe Kane, a consultant to the television industry. "They make the gray scale blue, they make the light output as high as it will go, and they quite often use edge enhancement so that when you are far away it appears to have detail." Experts call this "torch mode," which may be effective on the salesroom floor but is painful for home viewing.

Most new TV's have options in the on-screen menu that can improve color fidelity. Dedicated settings like "sports," "cinema," or "vivid" alter color and brightness for specific viewing conditions.

Sports mode usually emphasizes greens, to make fields look spectacular. Vivid usually pumps up colors and brightness for watching in bright rooms. Movie or cinema mode is usually the closest to studio standards.

But even these settings do not necessarily produce the truest color. For that, you have to do the calibration yourself.

The simplest and least expensive way to calibrate a TV is to use the free THX Optimizer on any THX-certified DVD, like "The Incredibles" from Pixar. The DVD offers instructions on how to set color, tint, contrast and sharpness with on-screen tests.

"The procedures are basically the same we do on the master display monitor at the studio," said Rick Dean, vice president for technology development of THX, which has created certification standards for sound and picture in theaters and consumer electronic equipment. The optimizer works best with a $2 pair of blue-lens glasses available from the THX Web site (www.thx.com).

Sound & Vision magazine offers Home Theater Tune Up, a DVD with step-by-step instructions, tips and test patterns for adjusting the picture (www.soundandvisionmag.com, $21.95). But because it was produced in 2000, some of its advice might be outdated.

The Monster Cable I.S.F. HDTV Calibration Wizard (to be available this month at www.monstercable.com, $29.95) is even simpler to use. Instead of using test patterns, viewers watch video clips for adjustments. For instance, the viewer adjusts the black level until the lapel of a dark jacket onscreen is distinct from the dark shirt beneath it.

Another option, Joe Kane's Digital Video Essentials (www.videoessentials.com, $24.99), is up to date, but requires you to sit through lengthy explanations of how the tests work before you can use them.

The Avia Guide to Home Theater (www.ovationmultimedia.com, $49.99) has a great deal of information arranged in detailed menus so you can get an overview of a home theater setup, deeper information from submenus or skip right to the comprehensive collection of tests.

For the highest degree of picture accuracy, technicians certified by the Imaging Science Foundation use electronic color analyzers to adjust a TV to industry standards. The I.S.F. Web site, www.imagingscience.com, offers a list of technicians around the country who can perform this service.

Even after you have your TV calibrated properly, settings can drift over time, requiring readjustment. And sometimes a calibrated TV looks a little dull to viewers accustomed to torch mode. "Live with it a few weeks," Mr. Kane said, "then go back to what you used to watch. In most cases you'll say, 'Wow, this is awful.' "

The various devices that are hooked up to most TV's also affect picture quality. The cable box, DVD player, TiVo or digital video recorder - in addition to the TV - all have computer chips that process the video image on your screen.

The problem is these chips are not perfect, and each round of processing can add errors that diminish or distort the picture. The goal is to have the best-suited chip handle the processing, but how do you know which is best?

Only trial-and-error testing will tell. In most cases, the TV set has the best chips, but there are exceptions. To ferret out the superior chip you have to try various settings and connections.

For instance, you can connect a DVD player to your TV using a component cable. Component cables send an analog signal, which lets the TV do the bulk of the processing. Then for comparison, you can connect the same DVD player, set to progressive scan, using an HDMI or DVI cable, which transmits a digital signal largely processed by the player. Decide which connection gives you the better picture.

If it's too close to call, you can use the HQV Benchmark DVD from Silicon Optix (www.hqv.com/benchmark.cfm, $30), which has tests that reveal signal processing differences that may be subtle.

And if fine-tuning your set sounds too complicated, fear not. Even professionals like Scott Jordan, a home theater consultant with Electronics Design Group, say just about anyone can do it. "For the few hours it takes," Mr. Jordan said, "you'll have years of better TV."